1. Field of the Invention
The invention is in the area of the conveying of flat, bendable objects, in particular printed products, and relates to an apparatus according to the preamble of the independent Claim. Such an apparatus is disclosed, for example, in WO 2008/000099 A1 and EP 2 128 055 A2.
The apparatus serves for separating individual flat, bendable objects from the underside of a stack of such objects and for the onward conveying of the objects. The apparatus serves, in particular, for separating individual printed products from the underside of a stack of printed products and for the onward conveying of the printed products.
2. Description of Related Art
WO 2008/000099 describes an apparatus for separating individual flat, bendable printed products from the underside of a stack of printed products and for the onward conveying of the printed products. The apparatus includes a stacking area having a support region in which the stack is supported toward the bottom. The apparatus further includes a roller carpet having a plurality of rollers which are freely rotatable about their longitudinal axis, are moved past under the support region along a circular path and at the same time support the printed product stack toward the bottom. The rollers are fastened on a rotatable roller wheel or are coupled to the same for this purpose. In addition, the apparatus includes circulating separating and holding means in the form of suction elements and grippers which cooperate in pairs for separating the objects from the underside of the stack. The rollers are moved past under the stack in the support region in the same direction as the separating and holding means.
The apparatus also includes an onward conveying device for the onward conveying of the separated objects.
The removal of individual printed products occurs by a suction element, which is circulating in the support region, firmly attaching itself from below to the bottom-most printed product and removing the same downward by means of its circular movement. When the printed product is being removed, it is inserted by way of the leading edge into the gripper mouth of a gripper which is circulating in a synchronized cycle in the support region. The gripper grasps the printed product with a closing movement. In the same process step, a following support roller is moved between the underside of the stack and the removed printed product and peels said printed product from the stack during its movement through the support region.
Whilst the suction element is then released from the printed product and is moved away from the same, the circulating, closed gripper conveys the peeled-off printed product further downward toward an onward conveying device and transfers it to the onward conveying device. During this operation, the removed printed product is entrained in part into the inner region of the roller carpet and in this position is entrained a little bit further synchronously with the roller carpet before it is deposited onto the conveyor belt of the onward conveying device.
EP 2 128 055 A2 also describes an apparatus for separating printed products from the underside of a stack of printed products and for the onward conveying of the separated printed products. The apparatus includes a stacking area having a support region in which the stack is supported downward. In addition, the apparatus includes a circulating roller carpet having a plurality of rollers which are freely rotatable about their longitudinal axis, are moved through the support region and, at the same time, support the stack toward the bottom. In addition, the apparatus includes circulating separating and holding means in the form of suction means and grippers for separating the objects from the underside of the stack. The rollers are moved past under the stack in the support region in the same direction as the separating and holding means.
The apparatus also includes an onward conveying device for the onward conveying of the separated objects.
The rollers of the roller carpet are coupled to at least one roller wheel. The coupling is designed according to said embodiment in such a manner that the rollers are pivotable in relation to the roller wheel with their longitudinal axis.
The removal of individual printed products occurs by a suction element, which is circulating in the support region, firmly attaching itself from below to the bottom-most printed product and removing the same downward by means of its circular movement. When the printed product is being removed, it is inserted by way of the leading edge into the gripper mouth of a gripper which is circulating in a synchronized cycle in the support region. The gripper grasps the printed product with a closing movement.
Whilst the suction element is then released from the printed product and is moved away from the same, a following support roller is moved between the underside of the stack and the released printed product and peels the same from the stack during its movement through the support region. The circulating, closed gripper conveys the printed product further downward to an onward conveying device and transfers it to the onward conveying device. Said method steps correspond to the method described in WO 2008/000099. In the case of said operation according to the present embodiment, however, the removed printed product is guided completely into the inner region of the roller carpet.
The rollers, in turn, are pivoted by a control element in a release region of the circular path. This means that an opening, through which the onward conveying device is guided, is created in the roller carpet in the release region.
The printed product, which is conveyed completely into the inner region of the roller carpet by the gripper, is then guided out of the inner region through the opening in the roller carpet outside the region of influence of the rollers and transferred to the onward conveyor belt of the onward conveying device.
The disadvantage of the described apparatuses, however, is that the rollers support the stack of printed products during their movement through the support region only in a local manner, i.e. from point to point, and the linear support region is entrained correspondingly with the rollers through the support region.
If then, for certain reasons no printed products are removed over one or several cycles, i.e. so-called empty cycles are generated with non-occupied grippers, the stack underside can become increasingly curved due to the flexing of the support rollers which roll under the stack. An empty cycle is therefore characterized in that no product is sucked up and the corresponding gripper remains empty.
In the case of empty cycles, it is true that no object is removed from the stack by the suction element and the gripper, but the roller carpet continues to run past under the stack in the circulating direction. As a result of the rollers moving through the support region, the printed products bulge in a downwardly directed bag-like manner between in each case two rollers, which, when viewed over the support region, produces wave-like deformation of the underside of the stack. Said bulges are moved in each case together with the rollers in a wave-like manner through the support region in the circulating direction of the rollers. The operation connected thereto is called flexing.
Said unwanted effect occurs in particular with thin, not very rigid printed products and leads to mutual displacements of the printed products inside the stack. As a result faults can occur when separating the printed products by, for example, instead of individual printed products being separated off, several printed products are removed at the same time or by products being randomly, i.e. out of cycle, removed from the stack.
The bag-like bulging of the stack of printed products down through between the rollers also occurs on account of gravity when the apparatus is not moving, when the rollers are stationary in the support region. When the operation is resumed, the bulges are moved together with the rollers in a wave-like manner through the support region, which leads to the above-mentioned effect.